Gasoline engines



Nov. 1, 1966 Filed Nov. 2, 1964 E. BARTHOLOMEW GASOLINE ENGINES 8Sheets-Sheet 1 IFUGALAO CENTR ADVANCE NVENTDR:

ELU'ZBartholomew',7

VACUUM m H6 lp l5 Zaoo sooo ENGINE SPEED RPM ATTORNEY NOV. 1, '1966 E,BARTHOLQMEW 3,282,261

GASOLINE ENGINES 8 Sheets-Sheet 2 Filed Nov. 2, 1964 INVENTOR:EcULBczrthoZo/.new

ATTORNEY Nov. l, 1966 E. BARTHOL'OMEW GASOLINE ENGINES Fiied Nov. 2,1964 8 Sheets-Sheet 3 arZBgr/wlmew Nov. l, 1966 E. BARTHoLoMEw 3,282,261

GASOLINE ENGINES Filed Nov'. 2, 1964 8 Sheets-Sheet 4 l NVNTOR ECWLBUFHLolomew ATTORNEY NOV 1, 1966 E. BARTHoLoMr-:w 3,282,261

y'GASOLINE ENGINES Filed Nov. 2, 1964 8 Sheets-Sheet 5 INVENTOR: Ear'LBartholomew EQMWM 'ATTORNEY N0V- l, 1956 E. BARTHoLoMEw 3,282,261

GASOLINE ENGINES Filed Nov. 2, 1964 8 SheetsSheet 6 Qi y@ /NTAKEMAN/FOLD t940 BY MW ATTORNEY Nov. l, 1966 E. BARTHoLoMEw 3,282,261

GASOLINE ENGINES Filed Nov. 2, 1964 8 Sheets-Sheet, 'l

Il, l

TO SUCTION INVENTOR Earl Bartholomew ATTORNEY Nov. 1, 1966 E.BARTHoLoMEw 3,282,261

GASOLINE ENGINES Filed Nov. 2. 1964 s sheets-sheet a 501 `80E' 6g@ 60j650 604 7 l l Mw j 306 Y INVENTOR: Earlartholomeuf ATTORNEY UnitedStates Patent O This application is in part a continuation of priorapplications Serial No. 171,856 led February 8, 1962 (U.S. Patent3,171,395 granted March 2, 1965), Serial No. 301,- 249 led August 12,1963 (abandoned but replaced by Serial No. 445,856 filed March 29, 1965)and Serial No.

314,814 led October 8, 1963 (U.S. Patent 3,198,187 granted August 3,1965).

The present invention relates to gasoline engines7 and particularly toinduction and ignition systems used to supply the fuel-air mixture andthe ignition spark to the cylinders of these engines.

Among the objects of the present invention is the provision of novelinduction and ignition systems that are relatively simple yet provideimproved and more eiiicient engine operation.

The above as well as additional objects of the present invention will bemore fully appreciated from the following description of several of itsexemplications, reference being made to the accompanying drawingswherein:

FIG. 1 is a side view partly broken away of a gasoline engine accordingto the present invention showing the carburetor part of the intakemanifold and some control elements;

FIG. 2 is a graph showing a typical ignition timing arrangementexemplifying the present invention;

v FIG. 3 is a generally schematic illustration of the essential elementsof a gasoline engine having a dual induction system pursuant to thepresent invention.

FIGS. 4, 5, 6vand 7 are generally schematic illustrations of dual intakemanifold systems representative of the present invention;

FIG. 8 is a vertical sectional view partly broken away of theconstruction of FIG. 4 showing some of its internal details;

FIG. 9 is a generally schematic view -of a modified dual inducttionsystem illustrating another aspect of the present invention;

FIG. 10 is a sectional view of a carburetor control laccording to astill further modification of the invention; and

FIG. 1l is a vertical sectional view yof yet another induction systempursuant to the present invention.

According to the present invention a gasoline engine has a mixtureintake system connected to provide (a) a fuel-air mixture which undernon-choking conditions has an air-to-fuel Weight ratio not lower thanabout 14 except under high torque operation, (b) a throttle-closingcheck connected to limit the reduction of the rate of mixture o'w to theintake system to about 5-l0% per second when the throttle control isabruptly closed during high speed operation and the air flow ratereaches about 0.4 pound per |hour per cubic inch displacement, (c) anidle air flow rate about to 60% greater than minimum for no road loadwith 6 ignition advance before top dead center, and (d) ignition timingmechanism connected to retard the ignition to about 3 to 6 degrees aftertop dead center at idle, the timing mechanism having a vacuum advancesystem that provides essentially no vacuum advance when the throttle isin idle position.

The induction system can be arranged to heat the combustion mixture to atemperature of from about 160 to about 185 F. under light loadconditions inasmuch as this enables smoother idling and low poweroperation. Arrangements can be provided to reduce the mixture heatingunder maximum torque conditions or the like.

3,282,261 Patented Nov. 1, 1966 Setting the idle air ow rate to about 20t-o 60% above the rate ordinarily used is an important aspect of thepresent invention and it should be noted that the idle operation herereferred to is the equilibrium or so-called hot idle after the systemhas completed its warm-up. The fast or cold idle generally used duringwarm-up is only effective for a very short time to minimize stallingduring the period when the engine needschoking. It should be furthernoted that the higher idle air ow of the present invention is providedwithout increasing the idle r.p.m. to any significant degree or at all,as explained below, whereas the prior art cold idle has for its primarypurpose the increasing of the idle r.p.m.

Combining the throttle-closing check with the increased idle air flowenables combustion to continue during periods of deceleration,regardless of the speed from which deceleration begins. Because of thecontinued combustion there is very little unburned or partially burnedfuel components discharged through the exhaust during deceleration, thetime when the discharge'of such undesirable emission is generally manytimes as high as during engine operation at constant speed. This hasbeen the most diicult emission problem of the prior art and it issubstantially completely solved by the very simple combination ofincreased idle air ow and throttle checking.

It is preferred to use hydraulic throttle checking rather `than throttlechecking with a pneumatic dash-pot, al-

though both of them will give good results. Pneumatic dash-pots tend tobe more non-uniform, particularly where the throttle is closed withlarge variations in closing force, and will show -an undesirable initialrebound. Such rebound should be taken into consideration in providingthe 5 to 10% mixture reduction per second.

Checking can also be provided in other ways, as by applying the inertiaof a rotating mass geared to the throttle shaft to rotate at high speedduring the last few degrees of throttle closing. The inertia of suchmass keeps the throttle closing from being too rapid.

Another alternative checking technique is to have the throttle shaftgeared to a rapidly rotating vane whose rotation is slowed by airresistance as in a spring-wound musi-c box movement.

The addition of ignition retarding to the combination of high idle airilow and throttle checking provides good engine braking duringdeceleration without loss of combustion thoroughness. Engine braking islan important factor in practical automobile engines for example, andwithout it automobiles tend to be more difficult to control.

The further use of a lean fuel mixture with the foregoing combinationmakes the combustion so thorough that the exhaust shows exceedingly lowlevels of unburned and partially burned fuel ingredients duringdeceleration. An engine operated in this manner easily meets theemission limits set by the State of California in its anti-smogrequirements.

The foregoing features can be used with either single intake manifoldarrangements conventionally used in gasoline engines, or with theparallel-connected dual intake manifold arrangements described in theabove-listed prior applications, for example. Such dual intake mani-Ifold systems are diflicult to operate smoothly, particularly from acold start, unless there is adequate heating of the manifold that isonly opened for high power use. For acceptably rapid warm-up the highpower manifold has a heating surface or hot spot arranged to reach aternperature of from about 300 to about 450 F. when the engine isoperated from Ia cold start for `about 3 minutes under low-speed cruiseconditions. During low-speed cruise this heating will warm the stagnantcontents in the secondary manifold to an equilibrium temperaturegenerally in the `range of from about to about 225 F.

u The low power or primary manifold preferably provides a mixture supplypassageway with a cross-sectional area less than about Ss square inchlfor every 100 cubic inches of engine displacement, and is arranged tosupply mixtures having an air-to-fuel Weight ratio of at least about 14except under maximum torque conditions when the mixture can be richenedto -a ratio of from about 12 to about 12.8. The foregoing manifoldcross-section is adequate even when two successively firing cylindersare fed from the same manifold duct and have their intakes overlappingeach other so that the duct is loaded a little heavier than otherwise.The heating of the mixture in the low power manifold can be to atemperature of from about 140 to about 185 F., preferably between 140and 165 F. whether or not the high idle air rate and retarded sparkcombination discussed above is used.

According to lanother aspect of the present invention, the recirculationof exhaust to the intake manifold of a gasoline engine is throttled insuch a way as to cut off the recirculation when the mixture intakethrottle is at idle and to establish such recirculation lup to a maximumof 15% of the intake under all other throttle positions except at ornear maximum open position. Such recirculation is very simply providedby merely having a recirculation throttle mounted on the same shaft asthe principal throttle or the low power throttle in dual inductionsystems, so that both throttles operate together. The operation can beadjusted so that when maximum power is desired the exhaust recirculationis completely cut oif. At maximum throttle the combustion mixture isfairly rich and burns to give relatively small quantities of nitrogenoxides, so that exhaust recirculation is not needed then.

On the other hand, recirculation cut-off at maximum throttle is notneeded in dual induction systems inasmuch as the exhaust recirculationis preferably proportioned to the low power or primary induction portionand when the high power or secondary induction system is brought intooperation most of the induction takes Place through it so that theexhaust recirculation to the total intake is very small.

The interior of the secondary manifold should have a cross-sectionalarea at least as large as that of the primary manifold. By having theinterior of the secondary manifold substantially larger than that of theprimary manifold, the induction system will cause nearly all of thefuelair mixture to ow through the secondary manifold when the throttlingsystem controlling these manifolds is wide open. For example, when theinterior of the secondary manifold has a cross-sectional area about 21/2times that of the primary manifold, about 80 to 90% of the fuel-airmixture will flow through the larger manifold during maximum throttleoperation. Under such conditions it makes very little difference whetherthe smaller manifold is kept open or shut when the larger manifold is inuse. Substantial simpliiication in the controls is effected by leavingthe smaller manifold in use at all times.

Both manifolds of the dual induction systems of the present inventionare open to each other at each of the engines intake ports and theterminations of the primary manifold at each intake port are preferablyan average distance of about 1/3 to 1 inch from the intake valve seat.It is also very helpful to have the terminations of the primary`manifold above their respective intake valve seats.

The bypassing nature of the dual manifolds of the present invention alsoenables one manifold to act as equalizer for the other so that betterinduction is obtained, particularly with engines in which the suctionstrokes of adjacent positioned cylinders are not uniformly displaced. Ina V-S engine having the firing order 1-8-4-3-6-5-7-2 for instance, therewill be two pairs of adjacent cylinders whose intake strokes overlapthrough at least 90 of crankshaft rotation whereas other pairs ofcylinders adjacent to each other will have their intake strokes spacedby 90 of inactive intake.

The acceleration pump normally used in gasoline en- 4 gines to improvethe engines response to rapid opening of the throttle is not needed inthe primary manifold of the dual systems of the present invention. Sucha pump can be used in the secondary induction portion, however.

FIG. 1 shows an induction system having a single carbuertor 10 mountedon an intake manifold 12 and provided with a dash-pot 14 that acts as acheck on the closing of the throttle valve 16. The checking action ishydraulic in nature, provided by a body of liquid in reservoir 18 thatflows into the cylinder 20 through one-way valve 22 when a piston 24 ispushed out in the cylinder as by a compression spring 26. The piston hasa piston rod 28 that carries an externally projecting nose 30 ofpolytetrauoroethylene, for example, positioned in the path ofthrottle-operating arm 32 which is fixed to the shaft 34 that carriesthe throttle valve 16. A linkage 36 connected to arm 32 controls theoperati-on of the throttle valve.

Valve 16 is shown in idle position and is adjusted to provide an idleair flow about 20 to 60% greater than minimum for no road load with 6ignition advance before top dead center. This is arranged by keeping thevalve lips 3S, 40 from engaging the walls of the carburetor barrel 42,as by a conventional stop, not shown. The lenticular or crescent-shapedpassageways thus formed between the lips and the walls allow theappropriate How of air. An idle fuel supply arrangement shown asincluding needle-controlled idle hole 44 and transfer idle holes 46, 4Sare connected `to an idle fuel bleed passageway for this purpose.

The last 10 to 20 degrees of throttle valve closing is arranged to takeplace with the arm 32 pushing against the nose Si) of the check 14.During such closing the liquid in check cylinder 20 is squeezed backinto reservoir 18 through a bleed passageway 50 that restricts thethrottle closing rate to give the desired rate of air ilow lreductionmentioned above. A scavenging return as by means of a passageway openingat 52 in the lower portion of cylinder 20 outside the piston and at 54in the reservoir permits the return of any liquid that may leak past thepiston.

A vacuum supply hole 56 is also provided in the wall of carburetorbarrel 42, and communicates through conduit S8 to ignition timingmechanism such as the standard vacuum -control system of an ignitiondistributor. The vacuum hole 56 is so located that it is substantiallycompletely above the adjacent edge of throttle valve 16 when in idleposition, and very little vacuum is produced during idle. only providevacuum advance of the ignition when the vacuum in the control is greater(the pressure lower) than the small vacuum produced in hole 56 at idleas well as during at least the last vportion of a deceleration with thethrottle in idle position.

FIG. 2 shows one ignition timing relationship suitable for use inconnection with the construction of FIG. l. The basic timing of theignition of this engine is set at 5 after top dead center with aspeed-responsive advancing control such as the standard centrifugalweights and the vacuum-responsive advancing control described above. Thevacuum control is shown as beginning to produce an ignition advance whenthe vacuum reaches about 6 inches of mercury, the advance increasingwith increasing vacuum until at about 16 inches of mercury the ignitionis at about 20 degrees before top dead center. This makes a total vacuumadvance of 25 degrees. A limit is provided so that no further ignitionadvance is caused by additional increases in the vacuum.

Speed-responsive ignition advance is shown to start at about 600 r.p.m.engine speed, advancing it to 30 before top dead center at about 3400r.p.m. This makes a total speed-control ignition advance of 35. It ispreferred to have the speed-responsive ignition advance climb moresteeply at the lower engine speeds, and FIG. 2 accordingly shows thatthe ignition is moved to about 15 The vacuum control is also connectedto before topdead center when the engine speed reaches about 1600r.p.ri'i. At higher speeds the advance can be made uniform orsubstantially so. The ignition timing advance mechanism can lbeconnected in the usual Way so that the vacuum advance adds to thespeed-responsive advance and either will be effective regardless of theother. The vacuum control can alternatively be connected so that whenthe throttle is closed at high engine or road speeds, the centrifugaladvance is entirely or partially offset by a vacuum retard. Thisarrangement provides greater engine braking during deceleration and canbe provided by an auxiliary retard control connected for operation onlywhen the manifold vacuum reaches the particularly high levels (lowpressures) that it attains during deceleration from high or mediumspeeds.

The induction system of FIG. 1 is preferably arranged to provide arelatively lean fuel mixture under all except maximum torque conditions.A particularly eifective arrangement is to have the idle mixture about14 pounds of air per pound of fuel, with a main fuel jet providing amixture of about 14.5 :1 and a power jet that increases the richnessunder maximum torque conditions to 12.5 or thereabouts. This type ofoperation will give a very low order of emission in the exhaust ofunburned or partially burned fuel ingredients as well as of carbonmonoxide. A feature of this low emission is that it is extremely loweven during deceleration regardless of the speed from which decelerationtakes place. Abrupt closing of the throttle control from speeds of 3000r.p.m. -or even higher when an engine is used to operate an aut-omobile,for example, will cause the engine to keep firing during the resultingdeceleration. At the same time the ignition will be sharply retarded byabrupt loss of all vacuum advance and if desired by the `auxiliaryvacuum retard, so.that the power delivered by the engine duringdeceleration is sharply reduced and very effective engine braking isobtained.

Because of the relatively large opening of the lenticular passages ateach end of the throttle valve 16, these passages are not as subject tovariation through accumulation of deposits or the like, and the idlesystem described above does not need as many idle tune-ups as is found`desirable in conventional induction systems. However, if desired thethrottle valve can be arranged to completely close with the idle airprovided by a bypass as described for example in the above-identiedearlier patent applications.

The carburetor of FIG. 1 can be essentially the same as standardcarburetors and can havean accelerator pump to improve the acceleratingcharacteristics of the engine, although this adds measurably to thedegree of undesired emission discharged in the exhaust. Thethrottle-closing check can also be arranged to operate with liquid takenfrom the fuel bowl of the carburetor, as for example in the carburetorillustrated in Fig. 149 on page 67 of the 1963 Ford Galaxie and 1962-63Mercury Monterey Shop Manual Supplement, copyright 1962 by the FordMotor Company, Dearborn, Michigan.

The rate at which the mixture flow reduction takes place can be adjustedby varying the viscosity of the hydra-ulic check medium, the size of therestriction through which the medium is forced, the linkage thatactuates the checking piston, and the strength of the compression orreturn spring 26. The last two variables can also be arranged to varythe uniformity of the rate of mixture flow reduction. A uniformathrottleclosure rate is obtained during checking by keeping the force on thechecking piston uniform. To this end the -lever arm of arm32 can Ibemade substantially unvarying through the checking travel, and theactuating force of the throttle return spring (not shown) can be mademore uniform as by changing Iits component in the direction of motion.The tendency of this lever arm to increase in length with the retractionof arm 36 from the fully closed position illustrated in FIG. 1, forexample, can be compensated for by rounding the nose 30 so that thepoint of tangency of the arm on the nose remains on the same spot of thearm although the point travels along the surface of the nose. Thiscompensation is provided by the arrangement of FIG. 1. This arrangementalso shifts the component of the throttle-closing force so as tocompensate at least partially for the normal drop in the closing forceapplied by the throttle-closing spring as the throttle closes.

The throttle-checking of FIG. 1 can also be connected so that it isdisabled at low speeds, as described in application Serial No. 301,249.Such disabling can respond to low eng-ine speeds, or low speeds of anautomobile powered by the engine.

The minimum mixture velocity in the intake manifold of the inductionsystem of FIG. 1 is higher than that of standard engines used inautomobiles, even higher than those that are normally yoperated with arelatively fast or more powerful idle to make sure that power-consumingaccessories such as air conditioner pumps do not cause stalling. Ingeneral, the air flow increase of the construction of FIG. 1 is largerfor engines with fewer accessories of the foregoing power-consumingkind. In the case of an engine with an all-mechanical transmission theair ilow increase is preferably about 40 to 60%, whereas an engine withan automatic transmission can have an increase of only about 20 to 45%for best results. In either type of situation the increased flow rate isnot suflicient to give smooth operation with the lean mixtures that arepreferred, unless the intake mixture temperature is in the range ofabout 140 to about 185 F., preferably 160 to 185 F., at light load. Suchheating Ais readily obtained by suitable adjustment of the flow ofexhaust gases onto a heating surface in good heat-transfer relation withthe intake manifold, preferably just before it branches. The heating ofthe mixture can be effected in other Ways, but it is desirablycontrolled in the cony ventional manner so that increases in under-hoodtemperatures or the like will reduce the amount of exhaust or otherheating, thereby keeping the mixture temperature from getting too highwhen the engine is hot. It is also helpful to interconnect the throttlewith the heat control so that opening the throttle to the widest willcompletely close off the flow of exhaust through the heating path,

thereby increasing the volumetric efficiency of the engine at maximumpower operation. An extra linkage 60 as shown in FIG. 1 is connected tothrottle control 36 for this purpose.

Reduction tof undesirable emission from the exhaust under decelerationconditions is so sharp, even when used in automobiles having manual,that is all-mechani- `cal transmissions, that the improvement therebyobtained cannot be attained with fuel-cut-oif devices. Such devices may,for example, stop all ow of fuel into the carburetor throttle whendecelerating from high speed, but because combustion is also stopped thefuel in the mixture in the manifold before cut-off continues to passthrough the engine and produces a relatively high level of undesirableemission. The construction of FIG. 1 accordingly does not need any fuelcut-olic arrangement, and thus avoids some complexity.

Also because of the relatively high minimum air flow velocity in theinduction system, the throttle-checking described above Iis not verycritical in nature. So long as it begins to take eiect when the air owrate drops to about $40 pound per hour per cubic inch displacement andcauses further reduction to proceed at about 5 to 10% per second, thedesired results are obtained. Only about 5 to 10 seconds of checking isthus needed.

The foregoing induction and ignition combinations can also be used indual intake manifold systems such as those describe-d in thevabove-listed prior applications. A more simplified yet highly effectivedual intake manifold assembly is illustrated in FIG. 3. The assembly ofFIG. 3 has two carburetor barrels 132, 232 each terminating at its lowerend inra flanged connector 71, 72

for mounting `against intake manifold lopenings 61, 62 respectively. Attheir upper ends these barrels have choke valves 140, 240 which can beoperated in the conventional manner. Barrel 132 has a throttle valve 134connected forl rotation by shaft 104 which carries 4an arm 106 locatedoutside the barrel. Throttle valve 134 is arranged to seat directlyagainst the walls of barrel 132 when the throttle of the inductionsystem is to be closed, so that no significant ow takes place betweenthis valve and the walls of its barrel.

The iiow of idle air is arranged to take place through a hole 148,preferably round, punched or drilled through valve 134, or by anexternal by-pass that connects the barrel above the throttle valve withthe barrel below the throttle valve. Idle air flow can also be providedby a combination of hole 148 and external by-pass. As explained above,this arrangement shifts the idle air flow away from the lenticular orcrescent-shaped gaps usually provided between the ends of the throttlevalve and the walls of the barrel. Such crescent-shaped gaps are subjectto so much variation due to accumulation of deposits and/ or wear thatcontinual maintenance is needed to keep in proper adjustment theconventional idle systems that use such gaps.

Barrel 132 can have conventional gasoline supply arrangements for idlefuel, high speed fuel, and high power fuel, and these arrangements arenot illustrated. Reference is made to application Serial No. 301,249 foreffective supply arrangements, particularly one in which a main fuelsupply jet has an air bleed thermostatically modulated to enrich themain jet mixture when the ambient temperature is very low.

Carburetion barrel 232 is generally similar to barrel 132 except that itis shown somewhat larger in crosssectional area. Only a supply of highpower fuel is needed for barrel 232 so that a throttle valve 234 in thisbarrel can close against its barrel walls without any provision for aby-pass. Throttle valve 234 is controlled by an arm 206 arranged foractuation when throttle 134 is wide open and more power is called for.

Manipulation of the throttles is effected by a rod 92, one end 94 ofwhich is connected to the throttle control such as the accelerator pedalof an automobile in which the engine is mounted. The rod 92 passesloosely through two bosses 96, 98, each of which in turn has aprojecting stud 88 that is pivotally received in their respective arms106, 206. Rod 92 also has two collars 85, 86 xed in position as shown. Acompression spring 83 between collar 85 and boss 96 enables movement ofrod 92 toward the left as seen in FIG. 3, to rotate arm 106 around shaft104. A washer 81 can be inserted between the spring 33 and boss 96. Asthe rod 92 is moved more and more to the left, its collar 86 eventuallyengages boss 98 when throttle 134 is open wide. Further movement of rod92 to the left will then open throttle 234 while spring 83 compresses toallow the rod to move through boss 96 without disturbing the openposition of throttle 134.

A mechanical bias such as tension spring 84 urges throttle 234 towardfully closed position, and a separate bias such as spring S7 can be usedto urge throttle 134 closed. Spring 84 can be made more powerful thanthe bias for the throttle 134, so that the operator can tell when he isoperating the throttle pedal far enough to open the large inductionsystem. The degree of force required to open the large throttle can bemade such that the operator cannot readily maintain it open for a longperiod `of time so that the engine is more apt to be operated on thesmall induction system alone.

The carburetion assembly of FIG. 3 also includes a small pump 210 tomomentarily supply to secondary barrel 232 a small amount of additionalfuel each time the secondary barrel is brought into use. Pump 210 canhave a conventional accelerator pump construction with an intake 219opening into the liquid in carburetor 8 bowl 150, and a discharge line245 running into throat 232. A ball check 220 in the intake and anothercheck 221 in the discharge make sure the liquid is pumped properly andyet not permitted to be sucked into throat 232 when the pump is notoperated.

Pump 210 has a diaphragm 216 secured to a piston 231 carried by a pistonrod 230 slidably tted through the wall of the pump. The slidable ttingcan also act as a vent for the chamber around the piston rod, and aspring 238 in the cylinder urges the piston outwardly to bring the pumpinto position for a pumping stroke.

When the control operates to effect the opening of the manifold oflarger cross-section, rod 92 engages piston 230 and causes it tocompress its spring 233, squirting a single charge of supplementary fuelinto throat 232. Pump 210 will continue to operate as an accelerationpump for the larger manifold. When there is a return to the use of onlythe smaller manifold, rod 92 is disengaged from piston rod 230,permitting the piston to be pushed out by its spring 238. This drawsreplenishing fuel from the carburetor bowl through intake 219, and thepump is thus prepared for the next pumping stroke.

Pump 210 can be arranged to operate essentially only when shift-overtakes place to the larger induction system. This is readily accomplishedby arranging for the pump to have an extremely short stroke that iscompleted when the large throttle 234 is barely opened. Furthermanipulation of that throttle will then not pump any more fuel so thatpump 210 will not operate as an acceleration pump under those conditionsand will merely be a shift-over pump.

A single charge of about 1/2 milliliter of supplementary fuel per cubicinches of engine displacement, made when the manifold of largercross-section is brought into use, has been found to make particularlysmooth the change-over in engine operation, even when the engine isunder heavy load, without detracting significantly from the eiciency ofthe engine and without significantly increasing its emission of unburntand partially burnt fuel as well as of carbon monoxide. However, as muchas l milliliter can be used per 100 cubic inches of engine displacementwith very good results, and as little as 1/s milliliter per 100 cubicinches will give detectable irnprovement, although no extra fuelwhatever is needed to make the engine perform adequately.

It is not necessary to have a fixed quantity of supplementary fueldelivered by pump 210 each time the large throttle is opened. Thequantity can be varied as by means of a temperature responsive controlthat inserts a wedge-shaped spacer between the piston rod 230 andcontrol rod 92.

The engine operation shows no detectable roughness when the largemanifold is switched off by closing of the large throttle valve. Noaccelerator pump is needed for the small carburetor inasmuch as thesmall induction system has a cross-sectional area less than 5A; squareinch per hundred cubic inches displacement of total engine displacement,and the mixture ow is accordingly very rapid at idle even without thehigher air flow of the construction of FIG. l.

Throttle valve 134 is also arranged so that it cannot be abruptly movedinto its fully closed position. For this purpose a stop arm secured tothe throttle valve 134 cooperates with a dash-pot 182 having a plunger184 positioned for engagement by the stop arm as it approaches the fullyclosed position. The plunger 184 is secured to a diaphragm 186 thatdefines an air cushion zone 188 vented by a small opening 190. A spring192 inside the dash-pot urges the plunger outwardly to engage the stoparm, but is not strong enough to overcome the throttle-closing forces.The throttle will then move to its fully closed position only as fast asthe air cushion 188 is permitted to vent through opening 190. A fewseconds is thus required for the last few degrees of throttle closure.

9 The return of the plunger 184 by its spring 192 when the throttle isopened, can be made much more rapid and is preferably completed in abouta second or less so as to be prepared for another deceleration when itwill introduce another appropriate delay. This helps assure a minimum ofundesired emission products.

FIG. 3 `shows opening 190 to be incorporated in a check valve disc 191biased as by a spring against a stop that restricts outflow of air tothat opening but permits inflow of air around the disc. This willprovide the more rapid return of plunger 184.

Notwithstanding the relatively high speed with which a fuel-air mixturemoves through the primary manifold even at idle, this manifold can stillbe provided with heat- King sufficient to bring the mixture it conductsto a Wet bulb temperature of between about 140` .and 165 F. measuredonder light load at a branching point in the manifold. The temperatureof the mixture in the primary manifold can be as high as 185 F. but thelower range is preferred to give the smoothest operation combined withrapid warm-up.

It has generally been considered that Iheating requirements become lessand less acute as the velocity of the fue-l-air mixture increases. Thisis based on the observation that high velocities in the intake manifoldso speed up the movement of the vaporized fuel droplets and films thatbranching tends to take place more and more uniformly.

Pursuant to the present invention, however, the mixture in the primarymanifold is made quite lean at light load and at idle, and this leannessseems to entirely offset the equalizing effect of Ithe higher mixturevelocity.

The secondary manifold requires substantial heating, particularly toprovide quick warm-up. It has been discovered that heating the internalsurface of the secondary manifold so that it reaches a temperature fromabout 300 to 450 F. when the engine is opera-ted from a cold start forthree minutes under lowspeed cruise conditions, e.g. 20 miles per hour,is readily accomplished and is highly desirable. Such heating enablesvery effective and smooth operation when the secondary throttle isopened three minutes after a cold start with very little or no choking,even at ambient temperatures of F. As indicated above, this heating willwarm the stagnant contents in the secondary manifold to an equilibriumtemperature generally in the range of from about 170 to 225 F.

Although a pneumatic throttle check is illustrated in FIG. 3, hydraulicchecks of the kinds referred to above can be substituted.

FIGS. 4 and 8 show a dual inta-ke manifold assembly applied to a fourcylinder in-line overhead valve engine in which the cylinder head isindicated at 410. One side of the head has a series of openings 421,422, 423, 424, 425, 426 and 427 leading to or acting as ports for theintake and exhaust valves in the individual cylinders. Openings 421 and427 are exhaust ports for the end cylinders respectively, and `opening424 is an enlarged exhaust port which is common to the two centercylinders. An exhaust manifold 430 has flanged connections 431, 434 and437 secured as by the usual manifold mounting bolts to the cylinder head410 to collect the exhaust from all four cylinders .and deliver it toflanged exhaust pipe discharge 439.

Two intake manifolds 448, 450 are secured to the head 410. Manifold 450lhas a set of flanged connections 452, 453, 455 and 456 arranged to |beconnected with the upper portions of intake openings 422, 423, 425 and426 respectively. The lower or remaining portions of these head openingsare connected by extensions 442, 443, 445 and 446 to the main branches448, 449 `of intake manifold From FIG. 8 it will be noted that intakehead opening 422 is divided by a partition 412 into an upper intake port414 and a lower intake port 416. Connection 452 of the intake manifold450 leads directly into upper port 414, and connection 442 of int-akemanifold 440 leads directly into lower intake port 416. Both ports 414and 416 merge into .a comm-on intake chamber 418 adjacent t-he intakevalve seat 419.

Between branches 448, 449 of intake manifold 440 in FIG. 4, there is amounting connection 461 for a fuel-air supply barrel of a carburetor. Inthe same way another mounting connection 462 is provided, preferably inthe central portion 459 of intake manifold 450 for another barrel of acarburetor.

The central portions of both manifolds 440, 450` are shown as locateddirectly over the central portion of exhaust manifold 430` so .as tohave the exhaust manifold provide the heating for the intake manifolds.For greater effectiveness the central portion 459 of manifold 450 isplaced at a lower level than its head openings 452, 453, 455, 456 so asto bring it closer to the exhaust manifold even though openings 452,453, 455, 456 are some distance .above the exhaust manifold.Alternatively the exhaust manifold can be so shaped that its uppersurface is elevated where it runs lunder manifold 450 to bring thatsurface into good heating relation with that manifold.

The two carburetion barrels connected to mounting openings 461, 462 ofthe intake manifolds can be the two barrels of the carburetion assemblydescribed in FIG. 3 or any one of the parent applications Serial No.171,856, Serial No. 301,249 and Serial No. 314,814.

FIG. 5 shows a dual intake manifold modification suitable for use with aV-8 engine in accordance with the present invention. In thisconstruction there is a pair of primary manifolds 548, 549, eachidentical in configuration. Manifold 540 has branches 541, 542, 543, 544that run respectively t-o the intake ports of the outer two cylinders ofthe second bank .and the inner two cylinders of the first bank.Similarly, manifold 549 has branches 545, 546, 547 and 548 forconnecting respectively to the intake ports of the inner two cylindersof the second bank and of the outer two cylinders of the first bank.

Each primary manifold has an intake opening 530, 539 for connection toseparate carburetor barrels of a dual barrel primary carburetor, eachlbarrel of which can be identical to barrel 132 of the construction ofFIG. 3.

Directly under and extending beyond both ends of the primary intakemanif-olds is a pair of secondary manifolds 550 ,and 559. Manifold 550has branches 551, 552, 553 and 554 running to the intake manifolds ofthe inner cylinders of the first bank and of the outer cylinders of thesecond bank respectively. Manifold 559 conversely has branches 555, 556,557 and 55S, for the intake ports of the :inner cylinders of the secondbank and lthe outer cylinders of the rst bank, respectively. TheIbranches of the outer cylinders at the adjacent ends of the two bankscross over each other, and the cross-overs can be of either hand. Thatis, branch 554 can cross over the top of branch 558 or branch 558 cancross over the top of branch 554. The s-ame applies to branches 553 and557.

iInstead of having the carburetor connections of the secondary manifoldsin the central portions of the manifolds, they Iare shown at 561, 562 inthe portions of the secondary manifolds that extend beyond the ends ofthe primary manifolds. On each site 561, 562, connections are providedin a dual barrel arrangement and each barrel at each of these locationscan be identical to barrel 232 of the construction of FIG. 3. Location561 can have one of its barrel intakes 571 opening into manifold 55E)adjacent the location where branches 551, 553 join. Similarly, barrelintake 572 at location 561 opens into secondary manifold 559 adjacentthe location where 1 1 branches 556, 557 join. At location 562 one ofthe barrel intakes 581 similarly opens into branches 552 and 554 ofmanifold 550 while barrel intake 582 leads to branches 555 and 558 ofmanifold 559.

A heating jacket 52@ is shown as surrounding the entire central portionsof primary manifolds 540 and 549 as well as the central portions ofsecondary manifolds 55@ and 559, and provides the heating referred toabove. The jacket is conveniently connected as by ducts 521, 522 toexhaust ldischarge openings that are conventionally provided in eachbank of the cylinders.

The ends lof the primary manifold branches in the construction of FIG. 5are smaller in diameter than the ends of the secondary manifold branchesand the primary branch ends are shown as penetrating through the wallsof the secondary branch ends so that the primary ends are brought downto a level below that of the secondary ends internally of the secondarybranches. The effective lengths of the primary fuel supply paths arethereby diminished, as compared with running the ends around thesecondary manifold 'branches to get below them.

Three dual barrel carbuertors can be connected to the barrel intakeopenings of the manifold assembly of FIG. 5. A primary carbuertor ofthis type supplies the primary manifold intake openings 530, 539, andtwo secondary oarburetors of this type, one each at locations 561, 562supply the secondary manifold combination.

In accordance with the present invention other modifications of intakemanifolds are effectively used with V-8 type engines. For example, theprimary manifolds 540, 549 in FIG. 5 can be combined into a singlemanifold fed by a single barrel of a carburetor having eight branches,one for each cylinder. Another modification is the elimination of thecentral portions of secondary manifolds 550, 559 from the constructionof FIG. 5 and leaving the two carburetor barrel intake locations S61,562 disconnected from each other. At each such location, according tothis modification, each carburetor barrel intake opening supplies onlytwo cylinders. A further variation is to have at each location 561, 562only a single carburetor barrel intake opening leading to the fourcylinders at that end of the engine. In this single barrel variation thesingle barrels at each end of the engine can either be disconnected fromeach other, or they can be united through an equalizing conduit as inthe construction of FIG. 5.

The carburetor barrel intake openings at locations 561, 562 can also bemoved into positions adjacent the carburetor barrel intake openings 530,539 of the primary manifolds so that a unitary carburetor with anappropriate number of barrels can be mounted in place to supply all themanifolds. This combination is more readily eected when the equalizingconduits for the secondary manifolds are eliminated. In any event, bysuch bringing together of the various carburetor barrel intake openingsa V-8 engine can be equipped with just one triple barrel carburetorhaving one primary barrel for the primary manifold and two secondarybarrels, one for each barrel intake opening of the secondary manifoldcombination.

FIG. 6 illustrates a manifold assembly with a triple carburetor barrelintake. The primary manifold 640 is fed by a central barrel intake 630and two secondary manifolds 659, 659 have barrel intakes 661, 662,respectively, on either side of intake 630. To allow closerjuxtaposition the secondary manifolds are each made about twice as highas they are wide, and they each branch into upper and lower halves thatextend out to the respective cylinders. The upper half 611 of themanifold 650 terminates in branches 657, 658, whereas the lower halfends in branches 651, 652. A similar construction is shown for secondarymanifold 659.

There is no communication between the two secondary manifolds except byway of the branches of the primary manifold 640. These branches can beat a level low engine such as that illustrated in FG. 2.

enough to `directly penetrate into the corresponding ends of thesecondary manifold branches.

To make the mixture flow paths more or less equal in length for eachcylinder, the lower halves of the secondary manifold can be arrangedbelow the level of the cylinder intake ports so that the inner branches651, 652, for instance, extend upwardly before they reach the ports.This added upward distance plus the added distance the mixture travelsto reach the lower manifold half from intake 661, can be made to equalthe total travel distance through the upper manifold half.

The intake openings 661, 662, are also offset to correspond to theoffset orientation of the intake ports in a V-8 engine, for example, sothat these openings are in the longitudinally central portions of theirrespective manifolds.

The small manifold can have its branches lowered so as to be below theheating jacket 624i shown as enveloping the central portion of bothmanifolds. This reduces the heating of the primary manifold with respectto the secondary.

It is not necessary to have the primary and secondary manifold branchends adjacent each other at each cylinder. FIG. 7 shows an effectiveintake arrangement for an In the construction of FIG. 7 the intake valveseat 719 leads to an intake port or chamber 718 that divides into twobranches extending out different sides of the head. A primary branch 716is arranged for connection to a primary intake manifold on one side ofthe head, and a secondary branch 714 is arranged for connection to asecondary manifold on the other side of the head. Such branched intakeopenings can be arranged in heads even of the liquid-cooled overheadvalve type without significantly reducing the heat-transfercharacteristics of cooling jackets and the like.

It is desirable to have the fuel-air mixture conduit from the pri-maryintake manifold terminate at a location that averages about one-third toone inch from the intake valve seat. If the distance that separates theprimary conduit termination from the intake valve seat is madematerially larger than one inch, the liquid components of the mixturetend to be excessively deposited on the walls of the relatively largeopen end of the conduit for the secondary fuel-air mixture. On the otherhand, making the average distance between the valve seat and thetermin-ation of the primary fuel-air con-duit significantly smaller thanlone-thi-rd inch makes the construction awkward to manufacture.

The average distance referred to is the distance between the valve seatand the avera-ge level of the primary fuel-air mixture conduit opening,measured along a line connecting that average level with the nearestportion of the valve seat. For primary fuel-air mixture conduits ofcircular, square, eliptical Vor similarly symmetrical crosssections, theaverage level is the level of the center of such cross-sections.

The flow of unvaporized portions of the fuel-air mixture from thetermination of the primary conduit of the present invention into thevalve port is better when such flow is downhill than when it is uphill.Accordingly, overhead valve engines in which the intake valve seats arebelow the valve port or chamber from which they are supplied, arepreferred. A similar benefit is Iobtained with L-head type engines butin this arrangement the engine would be turned upside down, that is withits crank shaft up and its head down, and such an arrangement is notordinarily desirable in automobiles because -of the awkwardness intransmitting the power from the relatively high crank shaft to therelatively low location of the driving axles.

There seems to be no real limit to the minimum size of the primarymanifolds. Even if its internal opening is pencil-thin, it will supplyan adequate amount of fuel to operate high-displacement engines at fairpower out- 13 puts. Accordingly while the primary manifold isconveniently made with an internal cross-sectional area onefifth that ofthe secondary manifolds, it can be made substantially smaller thanone-fifth, as for example onesixth or one-seventh, particularly ifmaintenance provisions permit the removal of dep-osits that tend to formwithin the manifolds.

FIG. 9 illustrates the exhaust recirculation aspects of the presentinvention. Here a carburetor 910 which may be of the dual inductiontype, has a primary barrel 932 opening into engine intake manifold 949and controlled by throttle valve 934. Shaft 904 pivotally holds thethrottle valve 934 and is extended to 4hold an exhaust recirculationvalve in an exhaust recirculation line 942 that opens intake manifold940 to the engi-ne exhaust. The valves 934 and 944 are arranged to beoperated simultaneously as by arm 906 fixed to shaft 904 and controlledby an actuator rod 994 as in the construction of FIG. 3, for example.

The simultaneous action of the throttle and recirculation valvesprovides a very effective and practical exhaust recirculation control.At idle it is better to have no exhaustrecirculation, whereas at otherthrottle positions as much as 15% or so of exhaust recirculation can behandled to achieve sharp decreases in emission of nitrogen oxides. Byhaving recirculation conduit 942 with a cross-sectional area about 15 ofthat of the carburetor throat 932, such highly effective recirculationcontrol is very simply attained by the construction of FIG. 9. A venturi955 can be inserted in the recirculation conduit to even more closelyproportion the recirculation to the flow through the principal venturi945 in throat 932.

For maximum power output, it is desirable to shut off the exhaustrecirculation. To this end the construction lof FIG. 9 includes afurther control valve 964 that is normally open but is automaticallyclosed when the main throttle is wide open. An arm 926 is shown asoperating valve 964 and Imounted for engagement by the control rod 994when in the wide-open throttle position. By shortening arm 926 it can bemade to actuate valve 964 from fully open to fully closed as thecontr-ol rod moves the main throttle valve through only the last fewdegrees of opening. Alternatively the valve 964 can be arranged to beginto close only after the main throttle is wi-de open, as by having aresilient or overtravel connection between the main throttle and the-operating rod 994.

The foregoing arrangement can be used with an engine having a singleintake manifold, and will give very good results with no attention onthe part of the operator. For engines with dual induction systems as inFIG. 3, the manifold`940 can be the primary or low-power manifold andthe secondary or high-power manifold can be used without anyadditional'exhaust recirculation supply to it. The opening of thethrottles in both primary and secondary manifolds will cause at least80% or more of the combustion mixture to be carried by the secondarymanifold so that the exhaust recirculation to the primary manifold is ofless significance and the auxiliary recirculation valve 964 can beeliminated without greatly detracting from maximum power output. Where90% or more of the combustion mixture is delivered through the secondarymanifold, the power limitation resulting from elimination of valve 964is insignificant.

The combination of FIG. 9 can be used with the principal throttle valve934 arranged to completely close against the walls of carburetor throat932 for idle operation. In such an arrangement a by-pass as indicated at948 can be used so that valves 934 and 944 can be parallel, that ispositioned in oo-planar arrangement. On the other hand, principalthrottle valve 934 can be provided with a stop that keeps it fromengaging the Walls of throat 932 at idle, as in the construction ofFIG. 1. In that event it is preferred to have exhaust control valve 944tilted somewhat with respect to valve 934 t-o permit exhaust controlvalve 944 to completely close when valve 934 is in idle position. Only afew degrees of tilting is needed and this has no significant effect onthe exhaust recirculati-on. The slight reduction in the resultingrecirculation proportion can -be compensated if desired by suitablyenlarging `the cross-sectional area of the recirculation duct ascompared wit-h that of the intake manifold.

By combining the features of the apparatus of FIG. 1 with that of FIG.9, there is obtained an engine strikingly superior in its exhaustemissi-on characteristics. However, the features of the construction ofFIG. 9 can be used by themselves as well as with those of the dualinduction system of FIG. 3 or those of the above-referred to earlierpatent applications.

Where the increased idle air flow deceleration system of FIGS. l and 2is not used, it is preferred to incorporate a fuel cut-off decelerationsystem as described, for example, in applications Serial Nos. 301,249and 314,814. A modified form of such fuel cut-off arrangement isillustrated in FIG. 10 based on the prirnry fuel carburetorconstructions of FIG. 4 in application Serial No. 314,814.

As described in the last-mentioned application, the carburetor of FIG.l0 has a throat 132 connected to manifold 321, and with a venturi 336.Fuel is supplied from an inlet tube 354 to a float chamber 352 and fromthere through the combination of a main jet orice 358, a supplementaryjet orifice 331, and a power jet orifice 384. An idle fuel take-off 368branches from the main jet passageway and leads to idle discharge port341 controlled by adjusting screw 378, as well as to idle transfer port372. Throttle plate 134 closes against the wall of throat 132 and whenso closed shuts off all passage of air and fuel except for idle fuel andan idle air bypass 346.

F-low of fuel through the main jet orifice is also controlled by acut-off valve 162 which is operated by the automatic control 351connected through conduit 302 to the interior of manifold 321. A branch300 of that conduit is also connected to directly actuate a valve 396that controls the power fuel jet. This jet is modulated by atemperature-controlled air bleed 383, and a similar modulation can beapplied to the main or supplementary jets in place of or in addition tothe power jet. The modulation action as well as the operation of theother carburetor features are more fully described in application SerialNo. 314,814 and that description is hereby incorporated herein as thoughfully set forth.

Control 351 controls the application of suction from a suction source142 to a conduit 143 that operates cutoff valve 162. To this end lines142, 143 are connected through a slide valve 330 with a hollow interiorin which is slidably fitted a valve block 332 having a recess 340 thatspans the distance between the locations where lines 142, 143 open intothe valve.

Block 332 is actuated by a pneumatic cylinder that has a piston 171fitted to be moved to the left, as seen in FIG. 10, to compress biasingspring 168 when the vacuum in line 302 reaches a magnitude at which fuel'cut-off is to be effected. A piston rod 166 carried by piston 171 isshown as penetrating into the slide valve 330 and passing looselythrough a passageway 331 in the block 332. Collars 311, 312 are carriedby the piston rod and can be fixed or adjustably located on the rod toengage and move the slide block with a lost motion gap indicated by thespacing 314.

Asillustrated, cut-off valve 162 is biased towards cutoff position byspring 166, and the flow of fuel is cut offwhenever suction is notapplied to line 143. The development of relatively high vacuum inmanifold line 302 by an abrupt deceleration of an yautomobile operatedby an engine having the carburetor of FIG. l0, moves piston 171 to theleft carrying slide block 332 with it into the illustrated position.This disconnects the suction from line 143 and fuel is cutoff.

As deceleration proceeds, the vacuum in line 302 diminishes graduallyand piston 171 will slowly be forced to the right under the inuence ofits biasing spring 168. Spacing 314 permits the piston to move asubstantial distance before it begins to move valve block 332 to theright to apply suction to line 143 and open the cut-off valve 162.Biasing spring 168 is preferably arranged so that the fuel flow is notrestored until the deceleration proceeds to the desired extent. By theabove arrangement the lost motion of spacing 314 provides a controlhysteresis which is particularly preferred as compared with thefrictional type of hysteresis disclosed in application Serial No.301,249. The lost motion is subject to substantially no variation as aresult of temperature changes and the like, and can be accurately set inproduction.

Decelerations of automobiles should produce fuel cutoff only when thedeceleration is from relatively high speed, over miles an hour, in orderto keep the exhaust emission low, and the manifold vacuum changes duringsuch decelerations are somewhat critical. For example, decelerationsfrom about 30 miles an hour can increase the manifold vacuum to about 22inches of mercury so that the control 351 is preferably set to causecut-olf when the manifold vacuum reaches 221/2 inches. Duringdeceleration the manifold vacuum will drop to about 211/2 inches whenthe vehicle speed comes down to a satisfactory low level such as 18miles per hour, and control 351 is accordingly also arranged so that atthis level of vacuum the biasing spring 168 will push piston 171 to theright sumciently far to cause restoration of fuel ow. Before this levelof vacuum is reached, biasing spring 168 can push piston 171 a distancecorresponding to the lost motion.

Once the flow of fue-l is restored the lost motion will keep it frombeing cut off again until the manifold vacuum reaches the 221/2 inchlevel. Since this level is not reached when the automobile is operatedin any way other than deceleration from the appropriate high speed,there is no interference with the operation of the automobile. Thecutting off of fuel will also terminate and fuel flow will be restoredwhenever there is a power demand on the engine, as by opening of thecarburetor throttle. Such opening sharply reduces the manifold vacuum toa 'level well below 211/2 inches so that piston 171 is rapidly moved allthe way over to the right by its biasing spring. An automobile equippedwith a relatively large size engine can be operated in the above mannerby having the fuel cutoff respond to deceleration from at least about1200 r.p.m. with the cutoic terminating when the engine speed fallsbelow about 850 r.p.m.

FIG. 10 also shows control 351 connected to supply a small amount ofauxiliary fuel when a fuel cut-off is terminated. This additional fuelis provided by pump 110 operated by a separate suction line 141 that isalso under the control of slide valve 330. To this end valve block 332is arranged as in application Serial No. 314,814 to connect suctionsource 142 with line 141 when the suction source is disconnected fromline 143, and vice versa. The pumping of the fuel is more fullydescribed in the lastmentioned application and takes place through apump outlet 349 that opens into air bypass 346, preferably in arelatively wide portion 353 of the bypass with the stream of pumped fuel350 directed at a narrowed portion of the bypass.

The construction of FllG. 11 has a three-carburetorbarrel intake feedinga single induction manifold of a V-8 type engine. This induction systemhas a common passageway 800 branching to all cylinders, and a mu-ltiplecarburetion assembly connected to said passageway, said assemblyincluding one carburetor 811 having a venturi 821 with a cross-sectionalarea between about 5 and 30% that of the passageway. Four of themanifold branches or runners open at 801, 802, 8d3, 804 in one wall 806of the passageway, the remaining four opening in a similar manner in theopposite Wall and are not seen in the figure.

Two additional carburetors 812, 813 are connected to the passageway 800,and these carburetors can in general resemble the secondary carburetorsystem of FIG. 3. The secondary carburetors do not require an idle fuelsupply, idling of the engine being accomplished with the fuel mixturesupplied by the primary carburetor 811. The venturi 821 of the primarycarburetor has a cross-sectional area about 5 to 25% of the totalcross-sectional area of the primary and secondary fuel mixture supplies.The venturis 822, 823 of the secondary carburetors can, for example,each have a cross-sectional area twice that of the primary venturi.

An engine according to FIG. 11 will surprisingly enough operate verysatisfactorily under part throttle conditions with a fuel mixture leanerthan heretofore considered practical. Thus in a standard 1964 modelPontiac V-8 in which the standard two-barrel carburetor intake manifoldhas had its common wall, .a partition 1%@ inch deep by 1% inch longknown as the riser partition removed and the carburetor has beenreplaced with 4one that has a venturi 0.88 inch in diameter and adjustedto supply a mixture with a selectable ratio, very good operation wasobtained with air-to-fuel weight ratios as high as 15:1 and higher. Inthis configuration the venturi had a cross-sectional area about 11% ofthat of the cornmon passageway. Misring did not begin until the ratioreached about 17.5: 1, and the engine was judged suitable for generalpart throttle duty with a ratio of up to 16: 1.

The removing of the riser partition from the standard two-barrelcarburetor intake manifold converted it to one in which a commonpassageway branched to all cylinders. Before the riser partition wasremoved the same engine operating with the normal two low-speed barrelsof a standard four-barrel carburetor recommended for use with it wouldnot operate smoothly at part throttle with mixtures leaner than about14: 1.

The small venturi 821 of the carburetor 811 is the only one used at partthrottle operation, that is when the engine delivers a-ll the powerdemanded and the throttle of carburetor 811 is not open wide. Apparentlythe small size of this venturi provides a very uniform part-throttlemixture which distributes itself uniformly to the cylinders via a singlecommon passageway, particularly in a V-8 engine where the distributionis otherwise very poor. Although the common passageway is large enoughto adequately carry the much more concentrated fuel mixtures needed foroperation at maximum power, and the part throttle fuel mixtures are muchmore rareed, they still travel through the common manifold at a ratefast enough to achieve good distribution. It is the lack of gooddistribution in the conventional V-8 engines which leads to mixtureenrichment for the purpose of providing adequate performance from thecylinder receiving the leanest mixture as a result of the poordistribution.

The small venturi carburetor is the only one used at idle, and incombination with the single common manifold provides idle operationwhich is smoother than with the standard two-barrel carburetor and muchsimpler to adjust. Idling can accordingly be accomplished with theengine of FIG. 11, using idle mixtures of about 14.5 :1. The idleadjustment of two carburetor barrels each supplying half the cylindersas in the standard engine, is almost impossible to accomplish properlywithout a set of expensive instruments, whereas the accurate adjustmentof a single idle barrel as in the construction of FIG. 11, is readilycarried out with only a tachometer.

In the part throttle operation of the engine of FIG. 11, generally atspeeds of at least 1000 r.p.m., the automobile can be driven at aconstant speed as much as 75 miles per hour, so that most of the engineoperation is under such conditions. The emission of undesired productssuch as CO and unburned or partially burned hydrocarbons is sharplyreduced by the lean mixture operation under those conditions, and fueleconomy is correspondingly improved. In the standard engine describedabove hydroother hand the engine of FIG. 1l performed very smoothly atpart throttle with a mixture ratio of 16:1 and a hydrocarbon emission ofonly 112 parts per million. The comparable fuel consumption rates at1200 r.p.m. and horsepower output were 11.7 pounds per hour for thestandard engine as against 10.6 pounds per hour with the engine of FIG.11.

The heating of the induction mixture in the construction of FIG. 11 canalso be to between 140 and 185 F, and that ligure illustrates a ribbedhot spot 830 in the common passageway 800 and in good heat exchangerelation with a duct 840 that carries exhaust gases. The hot spot ispreferably directly under the small carburetor.

The larger carburetors 812, 813 are brought into use under high powerdemand as for example when the throttle of carburetor 811 is wide openand more power is needed. The controls for such purpose can be of thetype illustrated in FIG. 3, although there is no need for extra pumpingof fuel when the large carburetors are opened. Instead of having twolarge carburetors 812, 812, the high power mixture can be supplied byone large carburetor or by three or more carburetors, or even by fuelinjection combined with additional air supply means into the manifold orinto the intake ports or into the cylinders themselves. The largecarburetons need not be arranged downstream from the small carburetor,but can be connected transversely with respect to it. A conventionalacceleration pump does help the acceleration of the engine of FIG. 11.

In the foregoing combination of a 0.88 inch venturi with a modifiedPontiac intake manifold, the venturi provided a cross-sectional areaabout 0.10 of the total venturi cross-sectional area used for maximumpower in the standard engine. Also this was 0.11 of the crosssectionalarea of the common passageway in the manifold and about 0.16 square inchper 100 cubic inches of piston displacement. This latter proportion canvary from about 0.1 to about 0.2 square inch per 100 cubic inches ofpiston displacement. Inasmuch as about 70 horsepower can be obtainedfrom each 100 :cubic inches of displacement, this corresponds to 0.1 to0.2 square inch of venturi cross-section for every 70 horsepower ofmaximum engine output. Engines with a relatively large number ofcylinders such as 8cylinder engines or engines whose speed is limited torelatively low values such as large truck, bus orv industrial engineswill normally operate best near the low limit of this range while otherengines can make effective use of venturi sizes nearer the high limit.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed:

1. A gasoline engine h aving (a) a mixture intake system connected toprovide a fuel-air mixture Which underh` non-choking conditions has anair-to-fuel weight ratio not lower than about 14 except under hightorque operation and to maintain a tiow of fuel throughout alldecelerations, (b) a throttle-closing check connected to limit the Yreduction of the rate of mixture flow to the intake system to about5-10% per second when the throttle control is abruptly closed duringhigh speed operation and the air flow rate reaches about 0.4 pound perhour per cubic inch displacement, (c) an idle air flow rate about to 60%greater than the minimum for idling at no road load with 6 ignitionadvance before top center, and (d) ignition timing mechanism connectedto retard the ignition to about 3 to 6 after top dead center at idle,

said mechanism having a vacuum advance system that provides essentiallyno vacuum advance when the throttle is in idle position.

2. The combination of claim 1 in which the engine has a plurality ofcylinders and the intake system has an unbypassed manifold connected toprovide a mixture having a temperature of from about 160 to about 185 F.at light load.

3. The combination of claim 1 in which the throttleclosing check hasliquid dash-pot check mechanism.

4. The combination of claim 1 in which the engine has a plurality ofcylinders and the intake system has a'lowpower manifold bypassed by ahigh-power manifold, the low-power manifold being connected to provide amixture having a temperature of from about to 165 F. at light load.

5. The combination of claim 2 in which the intake system includesmechanism -connected to reduce the mixture temperature at maximum torquecondition.

6. A method for keeping a gasoline engine firing during rapiddeceleration from relatively high speeds while maintaining good enginebraking, which method comprises checking the rate of throttle closure sothat the reduction of the rate of mixture flow to the intake systern isabout 5 to 10% per second when the air flow rate reaches about 0.4 poundper hour per cubic inch displacement, limiting the shut-down ofinduction mixture flow to an air intake about 20 to 60% higher than theminimum for idling under no road load -with 6 ignition advance .beforetop center, retarding the ignition to reduce the engine power during thedeceleration, and maintaining the flow of fuel throughout thedeceleration.

7. An induction system for a multicylinder gasoline engine, said systemhaving first and second intake manifolds in reciprocally bypassingarrangement, the first manifold has an effective cross-sectional arealess than about 5%; square inch for every 100 cubic inches of enginedisplacement, a carburetion assembly is connected to supply to saidfirst manifold under non-choking conditions a fuel-air mixture varyingfrom an idle mixture of at least about 14 pounds of air per pound offuel to a power mixture of from about 12 to about 12.8 pounds of air perpound of fuel, the assembly including throttling elements connected tosupply a fuel-air power mixture to the second manifold only when theseelements call for at least about as much power as obtained when thethrottling of the supply to the first manifold is about at its minimum,and heating structure connected to heat the mixture in the firstmanifold to from 140 to 185 F., and to provide a heating surface forheating the mixture supplied to the second manifold to cause thatsurface to reach a temperature of about 300 to about 450 F. when thesystem is operated from a cold start for about 3 minutes under low-speedcruise conditions.

8. The combination of claim 7 in which the carburetion assembly isconnected to maintain the supply of fuelair mixture to the firstmanifold when the fuel-air mixture is supplied to the second manifold.

9. The combination of claim 7 in which the power mixture for the secondmanifold has no more than about 12.5 pounds of air per pound of fuel.

10. The combination of claim 7 in which the carburetion assembly isconnected to supply to the first manifold a mixture that is nottemporarily enriched by throttle-opening movements.

11. The combination of claim 7 in which the throttling elements includedelay structure connected so that when the throttle control is abruptlyclosed the throttled mixture delivery rate drops off about 5 to 10% persecond when it reaches about 0.4 pound per hour per cubic inchdisplacement.

12. An induction system for a multicylinder gasoline engine, said systemhaving first and second intake manifolds in reciprocally bypassingarrangement, the first manifold has an effective cross-sectional arealess than S; square inch for every 100 cubic inches of enginedisplacement, a carburetion assembly is connected to supply to saidfirst manifold under non-choking conditions a fuelair mixture varyingfrom an idle mixture of at least about 14 pounds of air per pound offuel to a power mixture of from about 12 to about 12.8 pounds of air perpound of fuel, said carburetion assembly being further connected to onlysupply to the second manifold a mixture of from about 11.5 to 12.5pounds of air per pound of fuel, and to shut off the supply to thesecond manifold except under maximum engine demand conditions, thesecond manifold has heating structure connected to provide a heatingsurface for heating the mixture supplied to the second manifold, and tocause that surface to reach a temperature of about 300 to about 450 F.when the system is operated from a cold start for about 3 minutes underlow-speed cruise conditions, the carburetion assembly maintains the owof fuel through all decelerations and includes delay elements connectedso that when the throttle control is abruptly closed the throttledmixture delivery rate drops off about 5 to 10% per second when itreaches about 0.4 pound per hour per cubic inch displacement and thefirst manifold has an idle stop that provides an air flow to the intakeabout to 60% greater than the minimum for idling under no road load With6 ignition advance before top center.

13. The combination of claim 12 and further including ignition mechanismconnected to provide no vacuum spark advance when the throttle controlis fully closed and to provide idle ignition about 3 to 6 degrees aftertop center.

14. An induction system for a multicylinder gasoline engine, said systemhaving first and second intake manifolds in reciprocally bypassingarrangement, the first manifold having a cross-sectional area smallerthan that of the second manifold, each manifold being connected to aseparate source of a fuel-air mixture including a throttle valve thatcontrols the supply of the mixture to that manifold, the cross-sectionalareas of the two manifolds being so related that when both throttles arewide open at least about 80% of the fuel-air mixture supplied forcombustion will pass through the larger manifold, a control assembly isconnected to keep the throttle for the second manifold closed under lowpower demand conditions and under all other conditions when the throttlefor the first manifold is not about fully open, the source of fuel-airmixture being connected to deliver to the larger manifold a fuel-airmixture richer than that delivered to the smaller manifold, and thecontrol assembly includes a pump connected to deliver additionalgasoline to the fuel-air mixture for the second manifold Whenever thethrottle for the second manifold is opened.

1.5. The combination of claim 14 in which the fuel-air mixture sourcefor the first manifold is connected to supply a mixture that is nottemporarily enriched by throttleopening movements.

16. The combination of claim 14 in which the control assembly includesdelay elements connected so that when the throttle control is abruptlyclosed the throttled mixture delivery rate drops off about 5 to 10% persecond when it reaches about 0.4 pound per hour per cubic inchdisplacement.

17. The combination of claim 14 in which the rst manifold has an idlestop that provides an air flow rate to the intake about 20 to 60%greater than the minimum for idling under no road load with 6 ignitionadvance before top center.

18. The combination of claim 14 in which the second manifold has heatingstructure connected to provide a heating surface for heating the mixturesupplied to the second manifold and to cause that surface to reach atemperature of about 300 to about 450 F. when the system is operatedfrom a cold start for about 3 minutes under low-speed cruise conditions.

19. The combination of claim 14 in which the control assembly includesautomatic structure to warn an operator when the throttle of the largermanifold is being opened, and to urge the last-mentioned throttle towardclosed position with a force sharply greater than it urges the throttleof the smaller manifold toward closed position.

20. In an induction system for a gasoline engine having athrottle-controlled mixture intake and an exhaust recirculation intake,the improvement according to which the exhaust recirculation intake isthrottled and such throttling is connected to cut off the recirculationwhen the mixture intake throttle is at idle and establish suchrecirculation at all other throttle positions except near maximum openposition.

21. A gasoline engine induction system having two intake manifolds inreciprocally bypassing arrangement, a rst throttle connected to supplyfuel-air mixture to one manifold for low power operation, a secondthrottle connected to supply a fuel-air mixture to the second manifoldfor high power operation, and additional throttle elements connected to(a) control recirculation of exhaust into the first manifold only, (b)shut off such recirculation when the first throttle is at idle position,and (c) establish such recirculation at about 15% as the first throttleis moved to near maximum open position.

22. The combination of claim 21 in which the first throttle has athrottle valve that is completely closed when at idle position, and therecirculation throttle elements include a similar valve aligned'with andoperated simultaneously with the first-mentioned throttle valve.

23. A fuel cut-off control for a gasoline engine, said control includingactuator means connected to detect the beginning of an abruptdeceleration from at least about 1200 r.p.m. and to only cut olf thesupply of gasoline to the engine in response thereto, said actuatormeans being further connected to terminate the fuel cut-off when theengine speed is below about 850 r.p.m.

24. The combination of claim 23 in which the actuator means is furtherconnected to terminate the fuel cut-off in response to any power demandon the engine.

25. The combination of claim 24 in which the actuator means includes aconduit for connection to the intake manifold of the engine, andmeasuring mechanism for measuring the degree of vacuum in the conduitand for controlling the fuel cut-off in response thereto.

26. The combination of claim 7 in which the first manifold has an idlestop that provides an air flow rate to the intake about 20 to 60%greater than the minimum for no road load with 6 ignition advance beforetop center.

References Cited by the Examiner UNITED STATES PATENTS 1,552,819 9/1925Brush 123-119 1,623,750 4/ 1927 Pingree 123-127 1,651,250 11/1927Brownback 123--127 1,680,373 8/1928 Francis 123--122 1,804,754 5/ 1931Edwards 123-127 1,860,641 5/1932 Woolson 123-119 1,916,952 7/1933Heitger 123-122 2,033,396 3/1936 Perrine.

2,732,038 1/ 1956 Olson.

2,807,457 9/ 1957 Brueder.

2,886,021 5/1959 Burrell 123-127 2,967,514 1/1961 Riester 123-127 X2,993,485 7/1961 Cornelius 123-97 3,003,488 10/ 1961 Carlson 123-1273,037,493 6/1962 Burch 123-52 MARK NEWMAN, Primary Examiner.

KARL I. ALBRECHT, Examiner.

A. L. SMITH, Assistant Examiner.

6. A METHOD FOR KEEPING A GASOLINE ENGINE FIRING DURING RAPIDDECELERATION FROM RELATIVELY HIGH SPEEDS WHILE MAINTAINING GOOD ENGINEBRAKING, WHICH METHOD COMPRISES CHECKING THE RATE OF THROTTLE CLOSURE SOTHAT THE REDUCTION OF THE RATE OF MIXTURE FLOW TO THE INTAKE SYSTEM ISABOUT 5 TO 10% PER SECOND WHEN THE AIR FLOW RATE REACHES ABOUT 0.4 POUNDPER HOUR PER CUBIC INCH DISPLACEMENT, LIMITING THE SHUT-DOWN OFINDUCTION MIXTURE FLOW TO AN AIR INTAKE ABOUT 20 TO60% HIGHER THAN THEMINIMUM FOR IDLING UNDER NO ROAD LOAD WITH 6* IGNITION ADAVANCE BEFORETOP CENTER, RETARDING THE IGNITION TO REDUCE THE ENGINE POWER DURING THEDECELERATION, AND MAINTAINING THE FLOW OF FUEL THROUGHOUT THEDECELERATION.
 20. IN AN INDUCTION SYSTEM FOR A GASOLINE ENGINE HAVING ATHROTTLE-CONTROLLED MIXTURE INTAKE AND AN EXHAUST RECIRCULATION INTAKE,THE IMPROVEMENT ACCORDING TO WHICH THE EXHAUST RECIRCULATION INTAKE ISTHROTTLED AND SUCH THROTTLING IS CONNECTED TO CUT OFF THE RECIRCULATIONWHEN THE MIXTURE INTAKE THROTTLE IS AT IDLE AND ESTABLISH SUCHRECIRCULATION AT ALL OTHER THROTTLE POSITIONS EXCEPT NEAR MAXIMUM OPENPOSITION.